Amphibians of North Africa

Daniel Escoriza, Jihène Ben Hassine

• Publisher: Academic Press
• Year: 2019
• ISBN:
  9780128158357
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

Amphibians of North Africa is a comprehensive compilation of available data on the amphibians and reptiles found in various ecosystems across North West Africa and parts of the Mediterranean region. It is essential to identifying and understanding the ecological role of regional herpetofauna and its conservational importance. It examines the biological origins and diversity of amphibians in North Africa, along with their diverse ecosystems, including deserts, grasslands and subtropical forests. The book features detailed descriptions of the adult and larvae stages of species, such as the North African fire salamander, the common painted frog, Brongersma's toad and the Mediterranean tree frog.

This book is a vital resource for herpetology and ecology students and researchers, helping them identify, understand and conserve these amphibians and reptiles in their various habitats across the North African and Mediterranean regions.

• Presents the only book on research and species recognition of North West African and Mediterranean amphibians and reptiles in all life phases
• Provides novel, iconographic material about little-known species
• Features helpful visuals, including ink-drawings, photographs of adult and larvae stages, habitat photographs and distributional maps

Chapter 1

Introduction

Abstract

Amphibians are a group of vertebrates that originated in the Paleozoic Era. North Africa has few species, but these belong to very divergent lineages. Most of the species belong to Eurasian groups that colonized the region through land bridges in the Miocene. No mass extinctions have been detected in the region, but some marginal populations became extinct recently. The prolonged droughts could affect the relict populations of tropical amphibians in the central Sahara.

Keywords

Evolution; fossil record; Batrachia hypothesis; Eurasian lineage; functional guilds; global decline

1 Amphibian evolution and diversity

Amphibians are a class within Chordata whose origin dates back to the Paleozoic Era. In the Late Devonian, crossopterygian fishes (lobe-fin fishes) developed anatomical traits which allowed them to temporarily use the terrestrial habitats that surrounded rivers and streams. These features included the development of lungs and four limbs (robust and modified fins, but without fingers), which support their body weights on land. Transitional forms such as Elpistostege watsoni and Tiktaalik roseae (found in Canada) and Elginerpeton pancheni (found in Scotland) were recovered in deposits from 375 million years ago (Ma) (Ahlberg, 1995; Downs et al., 2008; Schoch, 2014). More derived forms appear 365 Ma, which show more developed limbs with seven or eight fingers (Acanthostega gunnari, Ichthyostega; Carroll, 1988). Ichthyostega could possibly inhabit streams and use the contiguous terrestrial habitats, whereas A. gunnari could have been exclusively aquatic (Ahlberg et al., 2005; Clack, 2002).

In the Early Carboniferous period (359–318 Ma), several Tetrapodomorpha showed a mosaic anatomy, combining traits typical of amphibians along with those found in other Tetrapoda (e.g., Crassigyrinus, Eucritta melanolimnetes; Panchen and Smithson, 1990; Clack, 2001). During the Late Carboniferous/Permian (318–270 Ma), the first true amphibians appear (Marjanović and Laurin, 2008; San Mauro, 2010). The monophyly of modern amphibians (subclass Lissamphibia) is supported by shared synapomorphies: monospondylous vertebrae, short ribs which do not encircle the body cavity, pedicellate teeth, presence of granular and mucous glands in the skin, fat bodies associated with the gonads, and skull structure (Duellman and Trueb, 1986). However, there is still no consensus on whether modern amphibians have evolved from a temnospondyl or lepospondyl ancestor and about the phylogenetic relationships of extant groups of amphibians: Procera (salamanders and caecilians are monophyletic) versus Batrachia (salamanders and frogs are monophyletic) hypotheses (Ruta and Coates, 2007; Fong et al., 2012; Maddin et al., 2012).

Based on the Batrachia hypothesis, the separation between frogs and salamanders occurred during the Late Permian/Triassic (270–240 Ma; Marjanović and Laurin, 2013). The first transitional amphibians that shared some characters with Anura appeared in the Early Triassic in Madagascar and Europe (250 Ma), Triadobatrachus massinoti and Czatkobatrachus polonicus (Sigurdsen et al., 2012). These species retained several plesiomorphic characters, like a high number of vertebrae, but possibly they were capable of hopping or performing short jumps (Shubin and Jenkins, 1995; Evans and Borsuk-Bialynicka, 1998; Sigurdsen et al., 2012). Stem-frogs were recovered in Lower and Upper Jurassic deposits (200–190 Ma) in Argentina and Arizona: Vieraella herbsti and Prosalirus bitis (Notobatrachidae) (Gao and Wang, 2001). The first crown-group frogs Callobatrachus sanyanensis (Discoglossoidea), Eodiscoglossus oxoniensis (Discoglossoidea), and Rhadinosteus parvus (Pipoidea, Rhinophrynidae) were found in younger deposits in China, England, and North America (Upper Jurassic/Lower Cretacic, 168–125 Ma; Evans et al., 1990; Henrici, 1998; Gao and Wang, 2001).

Salamanders possibly evolved in Eurasia during the Middle Jurassic (165 Ma), although there is an older candidate (Triassurus sixtelae; 240 Ma, Kirghizistan). The remains of T. sixtelae were small in size and low ossified, possibly a larval specimen and not allowing definitive conclusions (Skutschas, 2013). During the Middle Jurassic, stem-group salamanders are known to occur in Central Asia (Karaurus sharovi, Kokartus honorarius, and Urupia monstrosa) and England (Marmorerpeton kermacki; Gao and Shubin, 2003). The first crown-group Caudata, the genera Chunerpeton (Cryptobranchoidea, Middle Jurassic) and Beiyanerpeton and Qinglongtriton (Salamandroidea, Late Jurassic) are known from exceptionally well-preserved fossils found in China (Gao et al., 2013; Jia and Gao, 2016).

Origin of north-west African amphibians

North-west African amphibians, despite the low number of species, represent very divergent evolutionary lineages (Fig. 1.1). Most of the species belong to Eurasian groups which migrated to north-west Africa from the Mediterranean peninsulas, using the land bridges established intermittently during the Miocene (Veith et al., 2006; Gibert et al., 2013). The exceptions are the Sahelian species (Hoplobatrachus occipitalis, Sclerophrys xeros) and Sclerophrys mauritanica, the only bufonid belonging to a tropical lineage present in the mesic belt of north-west Africa (Pramuk et al., 2008).

Figure 1.1 Evolutionary relationships (measured as divergence times, in Ma) of north-west African amphibians, based on published molecular analyses (Pyron and Wiens, 2011; Pyron, 2014).

The Salamandridae family evolved in Europe, as independently indicated by the fossil record and phylogenetic analyses (Zhang et al., 2008). The oldest salamandrid (Koalliella genzeli, a stem-group pleurodeline) has been recovered from paleocenic deposits (57 Ma) in France and Germany, but the origin of the family was older, possibly between 86 and 58 Ma (Roček, 1994a; Marjanović and Witzmann, 2015). In north-western Africa, the older salamandrid remains (Pleurodeles) were recovered in Early Pleistocene sites (Bailon et al., 2011). Alytidae are a basal group of anurans which include three extant genera (Alytes, Discoglossus, and Latonia; Pyron and Wiens, 2011; Biton et al., 2016). Fossils of alytids were recovered in Europe and Israel (Latonia; 22–0.12 Ma) and in Europe (Discoglossus, 23–0.12 Ma; Alytes 2.5–0.12 Ma; López-Martínez and Ruiz Bustos, 1977; Sanchiz and Adrover, 1977; Roček, 1994b; Rodríguez et al., 2011; Gardner and Rage, 2016). In north-western Africa, alytids (Latonia and/or Latoglossus) were found since the Miocene (Gardner and Rage, 2016). The family Pelobatidae comprises a single extant genus (Pelobates). Fossils of possible crown-group Pelobatoids were recovered in Cretaceous and Paleogene deposits in central Asia (Chen et al., 2016), Gobiates spinari (87 Ma) and Macropelobates osborni (30 Ma). In Europe, pelobatids are known since the Oligocene, Eopelobates (34–12 Ma) and Pelobates (28–0.12 Ma). Pelobates decheni found in Germany (25 Ma) could be the sister lineage of all the extant Pelobates (Chen et al., 2016). In north-western Africa, pelobatids were found since the Late Pleistocene (Stoetzel et al., 2010). The family Hylidae originated in America and invaded Eurasia in two separate migratory events, during the Paleogene and the Miocene (Smith et al., 2005). Hylids were recovered since the Pliocene in north-west Africa (Raynal et al., 1990). True toads (Bufonidae) originated in America (Baez and Nicoli, 2004), and migrated to Eurasia through the Beringian land bridge during the Paleocene (Pramuk et al., 2008). Fossils of bufonids were found in north-west Africa since the Miocene (Gardner and Rage, 2016). The older crown-group ranoids were found in Cretaceous deposits from Sudan, supporting the hypothesis of an African origin (Bossuyt et al., 2006). The Raninae group migrated to Eurasia about 65 Ma (Bossuyt et al., 2006). The genus Pelophylax evolved in Eurasia and migrated back to northern Africa during the Miocene (Lymberakis et al., 2007). Fossils of Pelophylax frogs were found in north-west Africa since the Early Pleistocene (Hossini, 2001).

Amphibian diversity

At this moment, 6973 species of Anura and 722 species of Caudata are recognized (Frost, 2018). Gymnophiona (209 species) are not treated in this section because it has no extant representatives in the study region (Frost, 2018). Caudata are mostly confined to the northern hemisphere (Wells, 2007). Shared-derived characters of Caudata are the presence of a developed tail, the similar length of all their limbs, presence of gills in aquatic larvae, presence of teeth on both jaws, the absence of tympanic ears, and presence of ribs (Duellman and Trueb, 1986). Caudata show the longest genomes among vertebrates (e.g., the genomes of Ambystoma mexicanum and Amphiuma means are 10 and 30 times larger than that of humans, respectively; Hartl and Ruvolo, 2011; Keinath et al., 2015). Salamanders are also unique among vertebrates by their early development of autopodial struc...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Preface and Acknowledgments
• Chapter 1. Introduction
• Chapter 2. Amphibians of north-west Africa
• Chapter 3. Ecology of amphibians in north-west Africa
• Chapter 4. Amphibian surveys
• Chapter 5. History of batrachology in North Africa
• Chapter 6. Identification keys
• Chapter 7. Species descriptions
• Chapter 8. North-western Africa amphibians
• Chapter 9. Amphibians of Mauritania and Egypt
• References
• Index